.content{
    width: 640px;
    height: 640px;
    margin: 30px auto;
    position: relative;
}
.btn{
    width: 100%;
    height: 100%;
    position: absolute;
    left: 0;
    top: 0;
    background-color: rgba(0, 0, 0, .3);
    z-index: 2;
}
.btn button{
    background: none;
    border: none;
    background-size: 100% 100%;
    cursor: pointer;
    outline: none;
    position: absolute;
    left: 50%;
    top: 50%;
}
.startBtn button{
    width: 180px;
    height: 70px;
    font-size: 25px;
    font-weight: bold;
    background-color: aqua;
    margin-left: -90px;
    margin-top: -35px;
    border-radius: 35px;
}
.pauseBtn{
    display: none;
}
.pauseBtn button{
    width: 180px;
    height: 70px;
    font-size: 25px;
    font-weight: bold;
    background-color: aqua;
    margin-left: -90px;
    margin-top: -35px;
    border-radius: 35px;
}

/*snakeWrap*/
#snakeWrap{
    width: 600px;
    height: 600px;
    position: relative;
    background-color: #225675;
    border: 20px solid #7dd9ff;
}
#snakeWrap div{
    width: 20px;
    height: 20px;
}
.snakeHead{
    background: url('../img/snake.png') no-repeat;
    background-size: 100% 80%;
    transform: rotate(-90deg)
}
.snakeBody{
    background-color: #9ddbb1;
    border-radius: 50%;
}
.food{
    background: url('../img/apple.png') no-repeat;
    background-size: 25px;
}
